From

Thank you

Sorry

The attacks on September 11, 2001 showed the world that the worst possible scenario can actually happen. Here's a look at how far we've come in the 10 years since -- and how far we have yet to go.

REUTERS/Sean Adair SVThis series of photographs shows hijacked United Airlines Flight 175 as it approaches and impacts the World Trade Center's south tower, bursting into flames and raining a hail of debris on lower Manhattan September 11, 2001.

Perhaps the single biggest change to emerge in the post-9/11 world -- prompted in part by later natural disasters such as Hurricane Katrina -- has been a new focus on keeping workers working when corporate systems go down.

The 9/11 attacks, coming just after the late '90s Internet boom, were a wake-up call for many IT managers who hadn't contemplated the possibility of their entire computing systems being destroyed without warning.

The Federal Communications Commission is pushing Next-Generation 9-1-1 (NG 9-1-1) systems, which use Internet standards such as IP to replace analog, voice-centric technology developed more than 40 years ago.

After five years of development, the Internet Engineering Task Force (IETF) is putting the finishing touches on a standard and an overall architecture that will support Internet-based emergency calling.